Concept cars are notorious for rarely making it to the street. But what about the enticing features that designers include in their dreamy visions of our automotive future? We combed through the files we've amassed at the show this week and come up with five features that don't stand a chance in hell of ever escaping the shimmering incubator of the world's design studios. Count 'em down, after the jump.

5.) Saab 9-4x BioPower: Stainless-steel ski rack. Sure, it looks fine, and having the titanium-carbon-fiber Rossignols on the roof is just too risky these days. But where will the douchebag couple who spends the eight hours to Vermont talking about their trip to St. Bart's sit? Think about it.

As part of its Ethanol extravaganza, GM showed off its Saab 9-4x BioPower concept, a preview of a…
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4.) Saturn Flextreme: Clamshell trunk. While shellfish and trunk space are both well liked, combining the two is a pipe dream that'll, unfortunately, never be fulfilled. Saturn designers deserve credit for out-of-the-mollusk thinking, though. Hiho!

Remember the Opel Flextreme that was shown off at Frankfurt? Yeah, here it is again, except it is…
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3.) Lincoln MKT: Those massive gauge tubes were reportedly inspired by Swarovski crystal. While they do add an upmarket, Ice Pirates ambiance to the Lincoln, no corporate lawyer in Scarsdale who's ever had a knock-down-drag-out with his spouse in the living room would risk another crystal decanter to the face, under any circumstances.

Just as predicted, the 2008 Lincoln MKT is the Ford Flex-based derivative, though with a wildly…
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2.) Maybach Landaulet: Rear-seat convertible top. When everything shakes out, the 2010s may be known as the decade robber barons returned to lord it over the faltering middle class. But will the new JP Morgans and Vanderbilts really want to be chauffeured al fresco? We're betting not. These days, the proles have guns and laser scopes.

So we were all teased with the Mazda Furai teaser photo a few weeks back — that's the concept…
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BONUS: One Feature Missing from a Detroit Concept Car: Hummer HX. Notwithstanding its visual connection to the Halo 3 Warthog fighting vehicle, the Hummer HX concept could be a great success on the dystopian streets of post-revolutionary America. But the kids would demand a turret mount, a glaring omission from the concept. Keeping the Covenant from attacking humanoid refugee shelters would be impossible without it.